So far, a laminated glass has been widely used as the automotive windshields or side-glasses, or architectural window glasses, or the like. As the representative of above-mentioned glass, there can be mentioned, a laminated glass produced by interposing an interlayer film for laminated glass between at least two transparent glass sheets to integrate them. Said interlayer film consists of plasticized polyvinylacetal resin such as polyvinylbutyral resin.
While laminated glass of this kind tends to break due to a shock, the interlayer film interposed between glass sheets will not easily break, and the glass will keep adhering to the interlayer film even after breakage. Thus the risks for scattering debris of broken glasses are so low that it will prevent people in automobiles or buildings from being injured by the debris of broken glasses.
Although a laminated glass has the excellent functions described above, generally there is a problem of being inferior in heat insulation.
Among the rays, the infrared ray having a wavelength of not less than 780 nm has small amount of energy of about 10% compared to the ultraviolet ray, but has great thermal effect, and also the infrared ray is absorbed into the substances increasing temperature by releasing from the substances as heat, so the infrared ray is referred as heat ray.
Thus, cutting-off the infrared ray (heat ray) from the automotive windshields or side-glasses, or architectural window glasses, that is, increasing heat insulation of the automotive windshields or side-glasses, or architectural window glasses may suppress increase in temperature in automobiles or buildings. As the insulated glass, for example, a heat ray cut-off glass can be commercially obtained.
The above-mentioned heat ray cut-off glass is the glass sheet coated with multi-layers of metal/metallic oxide by means of metal deposition or sputtering to insulate direct sunlight. However, since the multi-layer coating is poor in scratch from outside and inferior in chemical-resistance, it was necessary to laminate interlayers composed of, for example, plasticized polyvinylbutyral resin, or the like to give a laminated glass.
However, the heat ray cut-off glass laminated interlayers is composed of, for example, plasticized polyvinylbutyral resin or the like had some problems following below:    (a) it was expensive;    (b) the multi-layer coating was thick, so its transparency (visible light transmittance rate) was low;    (c) the low bond strength between multi-layer coating and interlayer film resulted in exfoliation or blushing of interlayer; and    (d) it inhibited electromagnetic wave from transmitting into automobiles or buildings, causing troubles with communicating facilities such as a cellular phone, a car navigation system, an automatic garage opener, an automated teller machine and the like.
There are several proposals to solve the problems described above. For example, a laminated glass produced by laminating metal-deposited polyester films between plasticized polyvinylbutyral resin sheets is disclosed in Japanese Patent Publication for Opposition 52093/1986, Japanese Patent Publication for Laid-Open 36442/1989, and so on.
However, the laminated glass has some problems in the bond strength between plasticized polyvinylbutyral resin sheet and polyester film, thus not only the exfoliation will occur on the interface of the laminated glass with a lapse of time, but also electromagnetic wave transmittance is not enough.
Moreover, a laminated glass produced by dispersing fine particles of heat insulating mineral materials into interlayer film for the purpose of giving heat insulation is proposed in (for example, Japanese Patent Publication for Laid-Open 259279/1996, and so on). It is expected that the heat insulation can be increased by inhibiting increase in temperature in automobiles or buildings with the blockage of the infrared ray by using these functional fine particles.
In kneading functional fine particles such as metal or metallic oxide into an interlayer film, deterioration of haze in a laminated glass is the problem. This deterioration of haze strongly depends on the particle diameter of metal or metallic oxide contained in an interlayer film, the bigger the particle diameter is, the greater the haze value is. The same problem occurs in kneading functional fine particles, thus a technique regulating the particle diameter of the primary particle is introduced (Japanese Patent No. 2715859).
However, in an interlayer film, no matter how much the particle diameter of the primary particle or particle diameter in the dispersion may be regulated, melt-kneading with an adhesive resin under heat in the preparation of film results in recohesion between the particles. As the result, the particle diameter of the functional fine particle is bigger than that of the primary particle or in the dispersion. That is, in the interlayer film, desirable is regulating not only the particle diameter of the primary particle or the particle diameter in the dispersion, but also the particle diameter of the functional fine particle in the film.
Since the penetration resistance is required for a laminated glass represented by a laminated glass for automobiles, only good haze is not enough to produce a laminated glass, and appropriately adjusting the bond strength with glass is needed. A dispersant is necessary to disperse uniformly fine particles such as metal, metallic oxide and the like in an interlayer film. However, the dispersant influences on the bond strength, and so the necessary bond strength may not be obtained. That is, there were problems that the dispersant used for dispersing fine particles in a plasticizer influences on bond strength between the glass and the interlayer film, causing exfoliation or reducing penetration resistance, and moreover, the bond strength may change with a lapse of time by bleeding of the dispersant.